title: FERM domain of moesin desorbs the basic-rich cytoplasmic domain of l-selectin from the anionic membrane surface.
abstract: Moesin and calmodulin (CaM) jointly associate with the cytoplasmic domain of l-selectin in the cell to modulate the function and ectodomain shedding of l-selectin. Using fluorescence spectroscopy, we have examined the association of moesin FERM domain with the recombinant transmembrane and cytoplasmic domains of l-selectin (CLS) reconstituted in model phospholipid liposomes. The dissociation constant of moesin FERM domain to CLS in the phosphatidylcholine liposome is about 300nM. In contrast to disrupting the CaM association with CLS, inclusion of anionic phosphatidylserine lipids in the phosphatidylcholine liposome increased the apparent binding affinity of moesin FERM domain for CLS. Using the environmentally sensitive fluorescent probe attached to the cytoplasmic domain of CLS and the nitroxide quencher attached to the lipid bilayer, we showed that the association of moesin FERM domain induced the desorption of the basic-rich cytoplasmic domain of CLS from the anionic membrane surface, which enabled subsequent association of CaM to the cytoplasmic domain of CLS. These results have elucidated the molecular basis for the moesin/l-selectin/CaM ternary complex and suggested an important role of phospholipids in modulating l-selectin function and shedding.
authors.affiliation: Aflac Cancer and Blood Disorders Center, Department of Pediatrics, Emory University School of Medicine, 2015 Uppergate Drive NE, Room 440, Atlanta, GA 30322, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Deng
authors.forename: Sungyun
authors.initials: S
authors.lastname: Cho
authors.forename: Renhao
authors.initials: R
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D024361:Amino Acids, Basic / Q000737:chemistry*; D000838:Anions / Q000737:chemistry / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D006801:Humans; D019041:L-Selectin / Q000737:chemistry* / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000502:physiology; D013050:Spectrometry, Fluorescence
chemical_list: D024361:Amino Acids, Basic; D000838:Anions; D002147:Calmodulin; D008051:Lipid Bilayers; D008081:Liposomes; D008840:Microfilament Proteins; D019041:L-Selectin; C071058:moesin
keywords: 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine; 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine; 1-palmitoyl-2-stearoyl-(5-doxyl)-sn-glycero-3-phosphocholine; 5-((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid; CaM; DoxylPC; GST; IAEDANS; PIP(2); PMA; POPC; POPS; PS; TMR; calmodulin; ectodomain shedding; glutathione S-transferase; juxtamembrane region; l-selectin; moesin; phorbol-12-myristate-13-acetate; phosphatidylinositol-4,5-bisphosphate; phosphatidylserine; protein–lipid interaction; tetramethylrhodamine-5-maleimide